In the metal plating arts, it has long been known that substrates of magnesium and magnesium alloys are among the most difficult metal substrates to be plated with other metals. A number of compositions and processes have been used in an effort to obtain a reliably good coating of various metals on substrates of magnesium and magnesium alloys. However, the coatings thus obtained have not been wholly satisfactory in terms of the quality of the formed layer on the substrate, in terms of the complexity of the process required or both. The quality of the formed layer has been unsatisfactory in one or more of adhesion, completeness of coverage, appearance or protection afforded to the substrate of magnesium or magnesium alloy.
Due to the fact that substrates of magnesium and magnesium alloys are such difficult metal substrates to be plated with other metals, there has been a long-felt, continuing need for improved compositions and processes for zincating such substrates. Despite the motivation and numerous attempts, the long-felt continuing need has not been satisfied and so remains.